The present invention relates generally to multicell electric storage batteries, especially block-type starter batteries having a common gas canal for releasing gases from the individual cells of the battery, through the block cover to the outside.
The operating circumstances of such batteries often prevent the free release of gases from the individual cells, either for safety reasons or simply because centralized gas removal to a defined location is desirable.
According to West German Registered Utility Model No. 8003 869, each cell of a six-cell battery is provided with a vent hole, and each vent hole has an individual, closed vent canal which extends within the cover of the block casing, parallel to the canals of the other cells. Each of the vent canals opens into a fine-pored filter, which is common to all cells. A gas-outlet chamber follows the filter to ventilate gases to the outside of the battery.
Such a gas-release system is suitable for the prevention of flashbacks and explosions of oxyhydrogen gases present in the battery due to ignition from outside influences, and also to prevent the propagation of flames from one cell of the battery to the next. However, such a gas-release system suffers from the disadvantage that the filter can become clogged by electrolyte particles originating from the gases released during overcharging.
DE-OS No. 23 58 417 shows yet another multicell storage battery having a "central gas-release system". In this battery, the individual gas spaces which are developed at the top of each of the cells are permitted to communicate with each other either through small openings provided in the cell partitions, above the electrolyte level, or via a central tube with small openings, which passes through the partitions. In either case, the space above the electrolyte level provides a gas-release chamber, and accumulated gases are removed to the outside either through a tube connection on the cover or through the central tube (which is open only at one end).
However, central gas-release, per se, is unable to prevent acid mist from being discharged along with the battery gases. Also to be considered is that a compact starter battery used in motor vehicles is made more inconvenient to handle if provided with a tube for carrying the acid mist to a less hazardous location. Moreover, the risk of oxyhydrogen-gas explosions resulting from sparks or flames generated in the vicinity of the battery are even greater at the central release point, because of the larger amounts of gas being discharged. Isolation of this point by flame-protection means, such as a frit, is already a known and practiced measure. However, the frit has the disadvantage that its pores also gradually become clogged by condensed moisture, so that unacceptably high pressures can eventually build up in the battery due to the blockage of the gas outlet.